import sys

import pygame

from bullet import Bullet

from alien import Alien


from time  import sleep



def check_keydown_events(event, ai_settings, screen, ship, bullets):
	"""键盘 按下"""
	if event.key == pygame.K_RIGHT:
		#向右移动飞船
		ship.moving_right = True
	elif event.key == pygame.K_LEFT:
		#向左移动飞船
		ship.moving_left = True
	elif event.key == pygame.K_SPACE:
		#创建一颗子弹， 并将其加入到编组bullet中
		fire_bullet(ai_settings, screen, ship, bullets)
	elif event.key == pygame.K_q:
		sys.exit()

def fire_bullet(ai_settings, screen, ship, bullets):
	"""如果还没有到达限制， 就发射一颗子弹"""
	if len(bullets) < ai_settings.bullets_allowed:
			new_bullet = Bullet(ai_settings, screen, ship)
			bullets.add(new_bullet)


def check_keyup_events(event, ship):
	"""键盘 抬起"""
	if event.key == pygame.K_RIGHT:
		ship.moving_right = False
	if event.key == pygame.K_LEFT:
		ship.moving_left = False


def check_events(ai_settings, screen, stats, sb, play_button, ship, aliens, bullets):
	"""响应按键和鼠标事件"""
	for event in pygame.event.get():
		if event.type == pygame.QUIT:
			sys.exit()

		elif event.type == pygame.KEYDOWN:
			check_keydown_events(event,ai_settings, screen, ship, bullets)

		elif event.type == pygame.KEYUP:
			check_keyup_events(event, ship)
		elif event.type == pygame.MOUSEBUTTONDOWN:
			mouse_x, mouse_y = pygame.mouse.get_pos()
			check_play_button(ai_settings, screen, stats, sb, play_button, ship, aliens,
				 bullets, mouse_x, mouse_y)




def check_play_button(ai_settings, screen, stats, sb,play_button, ship, aliens, bullets, mouse_x, mouse_y):
	"""在玩家单击play按钮时候， 开始新游戏"""
	button_clicked = play_button.rect.collidepoint(mouse_x, mouse_y)
	if button_clicked and not stats.game_active:
		#重置游戏设置
		ai_settings.initialize_dynamic_settings()

		#隐藏光标
		pygame.mouse.set_visible(False)

		#重置游戏统计的信息
		stats.reset_stats()
		stats.game_active = True


		#重置记分牌图像
		sb.prep_score()
		sb.prep_high_score()
		sb.prep_level()
		sb.prep_ships()

		#清空外星人列表， 和子弹列表
		aliens.empty()
		bullets.empty()

		#创建一群新的外星人， 并让飞船居中
		create_fleet(ai_settings, screen, ship, aliens)
		ship.center_ship()






def update_screen(ai_settings, screen, stats, sb, ship, aliens, bullets, play_button):
	"""更新屏幕图像，切换新屏幕"""




	#每次循环时都重绘制屏幕
	screen.fill(ai_settings.bg_color)

	

	#在飞船和外星人后面重绘 所有子弹
	for bullet in bullets.sprites():
		bullet.draw_bullet()

	ship.blitme()

	aliens.draw(screen)

	#显示得分
	sb.show_score()

	#如果游戏处于 非活动， 就绘制play按钮
	if not stats.game_active:
		play_button.draw_button()

	#让最近绘制的屏幕可见
	pygame.display.flip()



def update_bullets(ai_settings, screen, stats, sb, ship, aliens, bullets):
	"""更新子弹的位置， 并删除已消失的子弹"""
	#更新子弹的位置
	bullets.update()
	#删除消失的子弹, 避免继续消耗内存
	for bullet in bullets.copy():
		if bullet.rect.bottom <= 0:
			bullets.remove(bullet)
	#print(len(bullets))
	#检查子弹数量是否真的被 删除了， print（）比图形绘制更耗费性能

	check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship, aliens, bullets)


	


def check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship, aliens, bullets):
	"""响应子弹 外星人 的碰撞"""
	#删除发生碰撞的子弹 和外星人

	#检查是否有子弹击中了外星人
	#如果是这样的，就删除相应的子弹和外星人
	#分别遍历 子弹 和 外星人， 一旦重叠， 返回一个字典（键值对），true 表示是否删除子弹/外星人
	collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)


	if collisions:
		for aliens in collisions.values():
			stats.score += ai_settings.alien_points * len(aliens)
			sb.prep_score()
		check_high_score(stats, sb)


	if len(aliens) == 0:
		#如果整群外星人都被消灭， 就提高一个等级
		bullets.empty()
		ai_settings.increase_speed()


		#提高等级
		stats.level += 1
		sb.prep_level()

		create_fleet(ai_settings, screen, ship, aliens)

def get_number_aliens_x(ai_settings, alien_width):
	"""计算 每行 容纳的数量"""
	available_space_x = ai_settings.screen_width - 2 * alien_width
	number_aliens_x = int(available_space_x / (2 * alien_width))
	return number_aliens_x
		
def get_number_rows(ai_settings, ship_height, alien_height):
	"""计算屏幕可容纳多少行外星人"""
	available_space_y = (ai_settings.screen_height - (3 * alien_height) - ship_height)
	number_rows = int(available_space_y / (2 * alien_height))
	return number_rows






def create_alien(ai_settings, screen, aliens, alien_number, row_number):
	"""创建一个外星人并将其加入当前行"""
	alien = Alien(ai_settings, screen)
	alien_width = alien.rect.width
	alien.x = alien_width + 2 * alien_width * alien_number
	alien.rect.x = alien.x
	alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
	aliens.add(alien)


def create_fleet(ai_settings, screen, ship, aliens):
	"""创建 外星人 群"""
	#创建一个外星人， 并计算一行可容纳多少个外星人
	#外星人间距为外星人宽度


	alien = Alien(ai_settings, screen)
	number_aliens_x = get_number_aliens_x(ai_settings, alien.rect.width)
	number_rows = get_number_rows(ai_settings, ship.rect.height, alien.rect.height)


	#创建外星人 群
	for row_number in range(number_rows):
		for alien_number in range(number_aliens_x):
			create_alien(ai_settings, screen, aliens, alien_number, row_number)


def check_fleet_edges(ai_settings, aliens):
	"""有外星人到达边缘时， 采取相应的措施"""
	for alien in aliens.sprites():
		if alien.check_edges():
			change_fleet_direction(ai_settings, aliens)
			break

def change_fleet_direction(ai_settings, aliens):
	"""将整群外星人 下移， 并改变 方向"""
	for alien in aliens.sprites():
		alien.rect.y += ai_settings.fleet_drop_speed
	ai_settings.fleet_direction *= -1






def ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets):
	"""响应被外星人撞到的飞船"""
	if stats.ships_left > 0:
		
		#将 ship_left - 1
		stats.ships_left -= 1

		#更新积分牌子
		sb.prep_ships()

		#清空外星人列表，和子弹列表
		aliens.empty()
		bullets.empty()


		#创建一群新的外星人， 并将飞船放到屏幕底部中央
		create_fleet(ai_settings, screen, ship, aliens)
		ship.center_ship()

		#暂停
		sleep(0.5)
	else:
		stats.game_active = False
		pygame.mouse.set_visible(True)


def check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, bullets):
	"""检查是否有外星人到达了屏幕底部"""
	screen_rect = screen.get_rect()
	for alien in aliens.sprites():
		if alien.rect.bottom >= screen_rect.bottom:
			#像飞船被撞到一样处理
			ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)
			break



def update_aliens(ai_settings, screen, stats, sb, ship, aliens, bullets):
	"""检查是否位于边缘，，，并 更新 外星人群中所有的 位置"""
	check_fleet_edges(ai_settings, aliens)
	aliens.update()


	#检查 外星人 和飞船 之间的碰撞
	if pygame.sprite.spritecollideany(ship, aliens):
		#print("飞船和 外星人 撞在一起了hit！！！")
		ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)


	#检查是否有外星人 抵达屏幕低端
	check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, bullets)








def check_high_score(stats, sb):
	"""检查是否诞生了新的最高得分"""
	if stats.score > stats.high_score:
		stats.high_score = stats.score
		sb.prep_high_score()




